Patent GB-1407433-A (GB)
Title: Method of manufacturing articles
IPC: B29C48/38
Filed: 1972-11-13
Abstract: 1407433 Curing rubber-covered cores DAINICHI-NIPPON CABLES Ltd and MITSUBA MFG CO Ltd 13 Nov 1972 [11 Nov 1971] 52397/72 Heading C3E [Also in Divisions B5 and Hl] A pre-dried core of an electric cable or a tube, is provided with a cured coating of screw extruded rubber or plastics material (see Divisions B4-B5) which is cured by passage of the extrusion through a heating medium means in surroundings at atmospheric pressure. Numerous conventional materials and curing agents are specified, and the core may comprise a stranded bare conductor, a plastics or rubber layer covered twisted conductor strand plurality with, or without, jute filler, rubber or plastics tubes, or a multilayered cured rubber or plastics tube which may contain a spring between the layers. In the examples using a stated eutectic salt mixture for curing; (1), (2) and (6), a core of three electric wires each covered with natural rubber insulation and jute, is extrusion coated with either natural rubber compound of stated composition, or a polychloroprene rubber copound of stated composition; (3) and (5), a core of either three natural rubber insulated stranded conductors, or of a plurality of stranded copper conductors around which a paper tape is wound, is coated with the polychloroprene compound; (4), a core of seven stranded copper conductors is coated with an ethylene/propylene/diene terpolymer compound of stated composition. The pre-drying of the core by heating is effected to a temperature of not more than 90 C., and preferably not more than 60 C., lower than that at which curing is effected. The pre-drying may be effected batchwise, or by passage upstream if the cross-head through one or more circulating hot air, infra-red or electrical heaters, and the curing of the coated core is effected by passage of the core issuing from the cross-head through an atmospheric pressure heater which may comprise a bath of organic liquids, e.g. polyglycols, silicone or mineral oils, stated eutectic inorganic salt or metal mixtures, a hot air heater, or an ultrasonic high frequency heater. In the embodiments curing is effected in a liquid bath through which, as in Fig. 9, the coated core W makes a single passage through inlets and outlets 63, 65 defined between vertically separable slidable plates (77), Fig. 10 (not shown), and through which the liquid overflows into receivers 79 leading to a reservoir 82, heated by heater 81, to be returned to the bath by a pump 72 and temperature adjusting device 83. Alternatively, as in Fig. 5, the coated core W, after passage through an upper bath 60, passes through a lower bath 61 around wheels 66, 67, followed by a further passage through the bath 61. Alternatively, as in Fig. 7, the coated core may make a single passage through an upper bath 60, followed by a double passage through a lower bath 61 effected around wheels 66, 73 respectively rotating about horizontal and vertical axes, with the cured core leaving the lower bath 61 around a guide wheel pair 74 which is positionally adjustable to vary the curing time in the bath. Downstream of the curing bath, heating medium is washed from the coated core during passage through a washing device where the heating medium may be dissolved in by immersion in a liquid solvent therefor, or may be washed by liquid spraying, the washing liquid being removed at the outlet of the device by a squeezing device of cotton or silicone rubber foam. With a molten eutectic salt mixture as curing medium, washing is effected with water at 60 C. or higher, followed by brushing of the coated core surface, or the application of ultrasonic vibrations.